This invention relates to a device for driving motor-operated closure parts, especially on motor vehicles, having a protective system for interrupting the closing movement when an object is situated in the opening so as to be squeezed by the closing parts.
For a protection system against the squeezing of an object, which operates without additional components located outside the drive control, such as proximity switches, various solutions have been suggested. It is, for example, known (German Patent No. 1 110 282 and U.S. Pat. No. 4,220,900) to monitor the current of the driving motor for a closure part, such as a sliding roof, sliding-lifting roof or window of a motor vehicle and to evaluate the rise of the motor current, when an obstruction is encountered, in order to send a signal to the protection system for interrupting the closing movement. However, such a type of evaluation cannot prevent a considerable squeezing force from having already been exerted on the object to be protected, especially on fingers and other parts of the body, before the arrangement responds.
The invention, therefore, has a primary objective of creating a device that ensures increased safety and can be constructed with relatively simple means.
This objective is achieved by means of a speed transmitting means which detects the adjusting speed of the closure part in at least one range of the movement path of the closure part that is critical with respect to the squeezing problem and by means of an evaluating stage responding to the speed signal and/or its rate of change, for producing an obstruction signal that activates the protection system.
The invention is based on recognition of the fact that motor-driven closure parts, such as sliding roofs, motor vehicle windows and doors, apart from the initial acceleration and the final braking, are driven at an essentially constant speed. However, the speed of a closing part will suddenly decrease when the closure part encounters an object. A speed signal that is proportional to the closing speed, therefore, represents a reliable indicator of the danger that an obstruction has been encountered.
In accordance with a further feature of the invention, an actual-value position transmitting means is provided that detects the actual position of the closure part, and a differentiating stage is connected to said actual-value position transmitting means for forming the speed signal. In this manner, a speed signal can be obtained simply and reliably. In order to determine speed changes which indicate the start of an object being squeezed, the speed transmitting means is expediently provided with a differentiating stage for forming an acceleration signal that corresponds to the acceleration or deceleration of the closure part.
The position signal and the signals derived from it, i.e., preferably the speed signal and the acceleration signal, are not influenced by disturbances, such as the ambient temperature, the condition of the driving mechanism and the motor current. However, in order to, in the case of voltage fluctuations which occur frequently in the case of motor vehicles, be able to differentiate clearly between the possibility that an object is being squeezed and the alternative possibility that a voltage drop has occurred, the evaluating stage may advantageously also be acted upon by a driving current or a driving voltage signal coming from a transmitting means detecting the current or the driving voltage of the driving motor.
Closure parts, such as a sliding panel and windows or doors of motor vehicles, as a rule, when attaining their closed position, are pressed against a sealing means or similar means which decrease the closing speed, without the continued existence of a danger that such occurred due to an object having been encountered. In order to avoid an undesirable response of the protection system during such final stages of movement, a further aspect of the invention lies in the response sensitivity of the protection system being changed as a functional of the actual position of the closing part. The arrangement may, for example, be made in such a way that the protection system is deactivated in at least one predetermined range of the path of movement of the closing part.
Changes of the speed of movement of a closure part that are caused by possible disturbances during an opening movement, in contrast to speed changes occurring during a closing movement, do not represent the danger that an obstruction has been encountered. In order to ensure that the protection system is activated only during a closing movement, the evaluating stage, expediently, has a logic circuit for recognizing a closing movement.
In the case of known sliding/lifting roofs, starting from a positive where the roof opening is fully closed by a roof panel, opening movement of the roof panel under action of the motor drive occurs in both directions, i.e., one direction for tilt-out lifting of the roof panel and an opposite direction for sliding retraction. In such a case, the evaluating stage preferably has a logic circuit for differentiating between the tilt-out lifting and sliding ranges.
The evaluating phase is advantageously provided with circuit components for suppressing insignificant signal fluctuations. In particular, these may be window comparators.
The drive advantageously, in a known manner (U.S. patent application Ser. No. 530,714) is part of a control circuit provided with a desired-value position transmitting means which compares the position of the closing part selected at the desired-value position transmitting means with its actual position and adjusts the position of the closing part until the deviation has become zero.
The arrangement can be designed so that the drive is stopped in response to an obstruction signal; however, a preferred design is to reverse the drive in response to the obstruction signal, i.e., automatically change the drive operation from a closing movement to an opening movement.